1. Field of the Invention:
The present invention relates to a vertical, collector-type high-pressure feed water preheater, with desuperheater and a device for separating the steam and water phases.
2. Description of the Prior Art:
In steam power plants, the feed water, which is maintained at a super-atmospheric pressure, is heated to the desired final temperature in high-pressure preheaters by means of steam which is bled from the turbines.
If, as is usually the case, the bleed steam is superheated steam, it is then possible to impart a portion of the superheating heat to the feed water, in a desuperheater which, viewed in the direction in which the feed water to be heated is flowing, encloses the end portion of the preheater tube-bundle, the steam flow-paths, along the tubes in the desuperheater, being provided by means of guide plates. At the end of that portion of the feed water tube-bundle through which it flows in a counter-current direction, the steam enters the condensation section, where it is condensed.
If, as the steam emerges from the desuperheater, the steam velocities are locally high, the preheater tubes suffer erosion damage as the steam collides with the condensate which is trickling down from the tube-bundles. This process endangers the tubes of preheaters in which the steam flows upwards, but the tubes of preheaters in which the steam flows downwards are also at risk.
Feed water preheaters are known which possess desuperheaters which are open in the upward direction, or which are only partially closed, so that the steam can flow out, upwards, at a high velocity and, at the same time, can carry the condensate formed in the upper portion of the preheater upwards, which causes erosion in that region. In order to reduce the velocity at which the steam leaves the desuperheater, an aperture has accordingly been provided, in a further design, in the dividing wall between the desuperheater compartment and the condensation compartment, this aperture being intended to shortcircuit a portion of the steam flow and to reduce the velocity of the remainder of the steam to the extent that the abovementioned erosion is largely prevented. However, this measure has led to more severe erosion in the condensation zone, since the steam flowing into this zone, through the abovementioned aperture, strikes condensate droplets which are even larger than those in the upper portion of the preheater tube-bundles.